Department of Mechanical Engineering, NIT Uttarakhand, Srinagar Garhwal, Uttarakhand-246174 India
Yogesh Kumar Prajapati
Department of Mechanical Engineering, NIT Uttarakhand, Srinagar (Garhwal) - 246174, India
Department of Mechanical Engineering, College of Technology, GBPUAT, Pantnagar, Uttarakhand-263145, India
In order to increase the heat transfer coefficient in conventional air heater, wire screen matrix is used as packing element which enhances the heat transfer coefficient of air. This results in higher outlet air temperature. The intermittent and variable nature of solar radiation needs a energy storage system in order to meet the demands at off sunshine hours; hence this wire screen matrix air heater is coupled with regenerator system in order to store the energy of hot outlet air. For analysing the packed bed regenerator using wire screen matrix air heater, energy balance equations have been analysed and reduced to partial differential equations in order to solve them using MATLAB. Most favourable value of pressure drop and charging time lies between mass velocity from 0.15 to 0.20 kg/m2-s in order to charge the rock bed at an average specific temperature of 35°C. Hence operating within this range of mass velocity, charging time and pressure will be 12600 sec (3.5 hours) and 46 N/m2 respectively corresponding to which efficiency is found to be 30.25%. Maximum charging efficiency is found to be 39.8% for the mass velocity of 0.05 kg/m2-s.
Comparison of different packing elements is also done to find out the best material for storage application in regenerator. It is found that the best material suited for storage application is concrete which is easily available and cheap. Charging and discharging profiles are drawn for different mass velocity for concrete. packed regenerator which facilitates the designer for estimating the maximum duration for room heating in night hours at desired temperature.